Note: Descriptions are shown in the official language in which they were submitted.
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Title: HEAVY DUTY PUNCH
This invention relates generally to a heavy
duty punch for piercing armor plate and the like, and
to a holder for the punch.
BACKGROUN~ AND SUMMARY OF THE INVENTION
At the present time, holes are formed in high
strength armor plate of the type used in tanks and other
military vehicles primarily by drilling, which is time-
consuming and expensive. Drills must be re-sharpened
or replaced after the formation of only a relatively
few holes. It is a principal object of this invention
to provide a heavy duty punch capable of forming large
numbers of holes in less time and hence at less cost,
to provide a punch which is durable and long-lasting and
to provide an improved holder for the punch.
The heavy duty punch of this invention is
adapted for piercing armor plate and the like. The
punch has a shank by means of which it may be held
during use. The punch also has a piercing end project-
ing axially from the shank. The piercing end is gen-
erally cylindrical and terminates in -a conical tip.
In the embodiments about to--ke described, the
dimensions of the punch are specified for optimum per-
formance, particularly with reference to the cone angle
on the piercing end of the punch, the curve connecting
the generally cylindrical surface of the piercing end
with the outer margin of the conical tip, and the flare
of the generally cylindrical surface of the piercing end.
Specifically, a heavy duty punch for piercing
armor is disclosed having a shank by means of which it
may be held when in use, and a piercing end projecting
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1 A
axially from the shank. The pi.ercing end terminates
in a conical tip having a cone angle of 169 to 176.
The piercing end flares in a direction tow~rd the conical
tip at an angle of 0 to 2 and merges into the conical
tip in a curve having a radius of .003" to .008".
Also in accordance with the specified embodi-
ments about to be described, the holder for holding the
heavy duty punch during a piercing operation comprises
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a body having a socket adapted to receive the shank of
the punch. Gripping jaws are provided to releasably
grip the shank. In one embodiment about to be described,
two guide slots in the body communicate with opposite
sides of the socket. The two jaws slidably mounted in
the respective slots are adapted to be advanced and re-
tracted into and out of gripping engagement with the
shank. In another embodiment, one jaw is fixed and the
other is slidably mounted. When the slidable jaw is
advanced, the slidable and fixed jaws cooperate in
gripping the shank of the punch. Means are provided
for selectively advancing and retracting the gripping
jaw or jaws.
Preferably, the shank of the punch is generally
cylindrical but tapers outwardly relatively to the
socket, and the shank-engaging surfaces of the gripping
jaws taper at the same angle as the shank in order to
have full surface contact therewith.
These and other objects of the invention will
become apparent as the following description proceeds,
especially when considered with the accompanying draw-
ings.
BRIEF DESCRIPTION OF T~E DRAWINGS
Fig. 1 is a sectional view of the heavy duty
punch and holder of this invention, taken on the line
1--1 in Fig. 2.
Fig. 2 is a view looking in the direction of
the arrow 2 in Fig. 1.
Fig. 3 is a fragmentary elevational view
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looking in the direction of the arrow 3 in Fig. 2
Fig. 4 is a view looking in the direction of
the arrow 4 in Fig. 1.
Fig. 5 is a detail view in elevation of the
punch.
Fig. 6 is a sectional view of a punch and holder
of modified construction, taken on the line 6--6 in
Fig. 7.
Fig. 7 is a view looking in the direction 7 in
Fig. 6.
Fig~ 8 is an elevational view looking in the
direction 8 in Fig. 7.
Fig. 9 is a view looking in the direction of
the arrow 9 in Fig. 6.
Fig. 10 is a detail view in elevation of the
punch in Figs. 6-9.
DETAILED DESCRIPTION
Referring now more particularly to the drawings
and especially to ~igs. 1-5, the heavy duty punch 10 is
mounted in a holder 12 carried by a ram 14 which is
reciprocable vertically above a table 16 on which a
work piece W, in this instance heat-treated, high
strength armor plate, is supported. When the ram
moves downwardly, the punch 10 in cooperation with
the die or button 18 in the table forms a hole in the
work piece and pushes a slug of punched out metal
through the central opening 1~ in the button.
The punch 10 is made of a suitable heavy duty
material such as tool steel and has a generally cylin-
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--4--drical shank 20 and a piercing end 22 projecting axially
fxom the shank. The specific dimensions of the punch
may vary, depending upon the hardness of the armor
plate. The punch 10 is designed to punch holes in
armor plate of somewhat less hardness than the armor
plate. The shan~ of punch 10, while generally cylindrical
actually tapers in an outward direction, that is in a
direction towards the piercing end. Preferably the
angle of taper is 0 15' as indicated in Fig. 5 of the
drawing.
The piercing end of the punch is generally
cylindrical, and its central axis coincides with the
central axis of the shank. The piercing end may be
truly cylindrical or it may flare in a direction toward
the tip from 0 to 2.
The piercing end terminates in a conical tip
24 in which the cone angle is 138 to 16Z. The gen-
erally cylindrical surface of the piercing end con-
nects with the outer margin of the conical tip in a
curve 25 having a radius of .003" to .008". The
piercing end blends into the shank in a flaring curve
of suitable radius where indicated at 26. The piercing
end preferably has a boron coated tip to increase the
hardness thereof, resulting in improved wear and anti-
galling properties.
There will be a clearance between the piercing
end 22 of the punch and the die opening 19. For
example, the diameter of the piercing end at its tip
may be .4" and the diameter of the die opening may be
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.475". Armor plate thickness may, for example, be in
a range irom 5/32" to 1/4".
The punch holder 12 comprises a generally
cylindrical body 29 having parallel flats 30 machined
or othen~ise formed in opposite sides beneath the base
32 thereof, which flats extend from the base to the
outer end of the body. Grooves 34 are machined or
otherwise formed across the full extent of the flats,
extending into the cylindrical wall portions of the
body beyond the ends of the flats. The bottoms 36 of
the grooves are preferably flat and parallel to the
flats 30, as shown.
The punch holder 12 has a cylindrical socket
38 in the outer end, the central axis of which coincides
with the central axis of the cylindrical body 29.
Slots 40 and 42 are machined or otherwise formed in
the body 29 of the punch holder and extend from the
bottoms 36 of the grooves 34 through the cylindrical
wall of the socket 38. These slots are aligned with
one another and open into the socket at opposite sides
thereof.
- Gripping jaws 44 and 46 are slidably mounted
in the respective slots 40 and 42 for radially inward
and outward movement relative to the socket. These
jaws have concave gripping surfaces 48 and 50 adapted
to grip and hold the shank of the punch 10 received
therein. The gripping surfaces 48 and 50 are tapered
and contoured so as to match the generally cylindrical
but slightly tapered side wall of the shank so that in
the inner or advanced positions of the gripping jaws
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the surfaces 48, 50 engage the wall of the shank in
full surface contact therewith. The gripping surfaces
48, 50 may, for example, be formed of electroplated
carbon steel for improved gripping.
The gripping jaws 44 and 46 are generally T-
shaped as seen in Fig. 2, each having a cross h'ead
portion 52 on the outer end. Coil springs 54 compressed
between the body 29 and the head portions 52 of the
gripping jaws urge the gripping jaws outwardly to re-
tracted positions in which the gripping surfaces 48, 50
are withdrawn from contact with the shank of the punch.
Camming members 60 and 62 are provi'ded for
camming the gripping jaws 44 and 46 radially inwardly
to their advanced positions shown in Fig. 1. The
camming members'are elongated pins mounted for sliding
movement in the parallel passages 64, 66 which extend
across the slots 40, 42 at right angles thereto. ~uch
pins extend through openings in the gripping jaws and
have tapered side surfaces 68 engagable with corres-
pondingly tapered side surfaces in the openings so
that when the pins are moved in an outward direction
the gripping jaws are cammed radially inwardly to the
advanced Fig. 1 position in which they firmly grip
the shank of the punch, The camming members have piston
heads 70, 72 reciprocable in hydraulic cylinders 74,
76 formed in the body 29 of the punch holder. The
camming members 60, 62 are retracted by means of coil
springs 78 compressed between the piston heads ana the
bottoms of the hydraulic cylinders. The camming
members 60, 62 are forced outwardly to their advanced
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positions shown in Fig. 1 against the action of springs
78 by hydraulic fluid pressure supplied to the head ends
of cylinders 74, 76 by the hydraulic pump system S.
The body 29 of the punch holder has holes 85
to receive fasteners which secure it to the ram.
The ~esign of the punch results in excellent
wear and anti-galling properties.
- In use, the hydraulic fluid pressureis re-
lieved to allow the camming members 60 and 62 to be
retracted by the force of springs 78 and the gripping
jaws 44, 46 ~o be retracted by the force of springs 54.
The shank of the punch is then inserted into the socket.
Hydraulic fluid pressure supplied to the cylinders 74,
- 76 causes the gripping jaws to be advanced by the
camming members into gripping engagement with the shank
of the punch. The gripping surfaces 48, 50 being con-
toured and tapered to match the cylindrical surface of
the shank permits full surface to-surface engagement
between the gripping surfaces and the cylindrical sur-
face of the shank. Due to the taper of the shank and
the gripping surfaces and the force of the hydraulic
pressure on the camming members, the shank is firmly
and positively held against accidental withdrawal from
the socket.
When the ram is operated to cause the punch to
descend rapidly, the piercing end of the punch drives
through the work piece W punching a slug of metal
through the opening in the die and forming a hole in the
work piece. Reversal of the ram causes the punch to
withdraw from the work piece and, as stated, the firm
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--8--
and ositive grip of the jaws on the punch shank insures
that the punch will withdraw cleanly fro~. the work
piece and continue to be firmly gripped in the holder.
The punch can be replaced when desired quickly
ana easily by simply 1) relieving the hydraulic fluid
pressure resulting in immediate release of the old punch
through the action of springs 54 and 78, 2) removing
the old punch and substituting a new one, and 3) re-
applying the hydraulic fluid pressure to clamp the new
punch in the socket of the holder.
A modification of the invention is shown in
Figs. 6-10~ The heavy duty punch 110, which is similar
to punch 10 but somewhat different in dimension, is
mounted on a holder 112 carried by a ram 114 similar to
the one previously described which is reciprocable
vertically above table 116 on which a work piece W'
is supported. The action is the sa~e as in the
previous embodiment, that is when the ram moves down-
wardly the punch 110 forms a hole in the work piece
and punches a slug of metal through the central opening
119 in the button 118.
The punch 110 is made of the same material as
the punch 10 previously described, but has specifically
different dimensions because of the somewhat greater
hardness of the work piece W', which again may be
armor plate. The punch 110 has a generally cylindrical
shank 120 and a piercing end 122 projecting axially
from the shank. Actually, although generally cylin-
drical, the punch shank tapers in an outward direction
towards its piercing end. Prefexably the anyle of taper
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is 1~ 30' as indicated in ~ig. 10 of the drawing.
The piercing end of the punch is generally
cylindrical and its central axis coincides with the
central axis of the shank. The piercing end flares
0 30' in a direction towards the tip.
The piercing end terminates in a conical tip
124 in which the cone angle is 169 to 176. The
generally cylindrical surface of the piercing end
connects with the outer margin of the conical tip in
a curve 125 having a radius of .003" to .008". The
piercing end blends into the shank in a flaring curve
of suitable radius where indicated at 126. The piercing
end preferably has a boron coated tip as in the case of
punch 10.
The same clearance between the piercing end of
the punch and the die opening, and the same armor plate
thickness may apply to this embodiment of the invention
as was specified for the embodiment of Figs. 1 to 5.
The punch holder 112 comprises a generally
cylindrical body 129 having a flat 130 machined or
otherwise formed in one side at the outer end thereof.
The punch holder 112 has a frusto-conical socket
138 in the outer end, the central axis of which coincides
w~th the central axis of the cylindrical body 129. The
side wall of the socket 138 is tapered and contoured so
as to match the generally cylindrical but slightly
tapered side wall of the shank of the punch.
A radial slot 140 is machined or otherwise
formed in the body 129 of the punch holder and extends
from the flat 130 through the side wall of the socket
138.
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--10--
A gripping jaw 144 is slidably mounted in the slot
140 for raaially inward and outward movement relative
to the socket. The radially inner or gripping surface
148 of the jaw is tapered and contoured similarly to
the wall of the socket so as to match the generally
cylindrical but slightly tapered side wall of the shank
so that in the inner or advanced position of the jaw
the gripping surface 148 will engage one side of the
shank in full surface contact therewith. The opposite
sidewall of the punch shank will be in full surface
contact with the socket wall, and hence the socket wall149
serves as a fixed jaw. I'he gripping surface 148 of the
jaw and the opposed socket wall may be formed of
electroplated carbon steel for improved gripping.
The slot 140 has a dove-tail configuration
and the main body portion of the gripping jaw 144 has
a similar configuration to retain the jaw and prevent
it from dropping out of the assembly.
The gripping jaw 144 is generally T-shaped,
having a cross head portion 152 on the radially outer
end. Coil springs 154 compressed between the body 129
and the head portions 152 urge the gripping jaw out-
wardly to a retracted position to release the shank of
the punch.
A camming member 160 is provided for camming
the jaw 144 radially inwardly to its advanced position.
The camming member is an elongated pin mounted for
sliding movement in the passage 164 which extends
across slot 140 at right angles thereto. The pin
extends through an opening in the yripping jaw and has
ll
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a tapered side surface 168 enga~eable with a corres-
pondingly tapered surface in the opening so that when
the pin is moved in an outward direction the gripping
jaw is cammed radially inwardly to the advanced Fig.` 6
position in which to firmly grip the shank of the punch.
The camming member 160 has a piston head 170 reciprocable
in hydraulic cylinder 174 formed in the body 129 of the
punch holder. The camming member is retracted by means
of the coil spring 178 compressed between the piston
head and the bottom of the hydraulic cylinder~ The
camming member 160 is forced outwardly to its advanced
position against the action of spring 178 by hydraulic
fluid pressure supplied to the head end of the cylinder
174 by the hydraulic pump system S'.
The body 129 of the punch holder has holes 185 to
receive fasteners which secure it to the ram.
~ ydraulic pressure supplied to cylinder 174 causes
the jaw 144 to advance, clamping the shank of the punch
between the gripping surface 148 of the movable jaw 144
and the o~posed side wall 149 of the socket which serves
as a fixed jaw. The tapered surfaces of the jaws and
the full surface contact they have with the punch shank
insures a firm and positive grip. ~hen the hydraulic
pressure is relieved, the jaw 144 is retracted and the
punch is released.
The operation of the embodiment of Fig. 6-10 is
the same as for the embodiment previously described.
Considering the prefered dimensions of punches
10 and 110 stated above, such dimensions fall in the
following ranges, namely: shank taper of 0~ 15' to
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-12-
1 30'; flare of piercing end in a direction toward the
tip o 0 to ~; conical tip cone angle of 138 to
176 and radius of curve connecting the generally
cylindrical surface of the piercing end and the outer
margin of the conical tip of ~003" to .008". All
dimensions within these ranges are operable and included
within the scope of this invention.
